1. Field of the Invention
The invention is directed to a beam splitter, preferably for optical positioning instruments such as multiaxis construction lasers or rotating construction lasers.
2. Description of Prior Art
In marking the alignment of tools and in marking of workpieces, particularly in the construction industry, there is a need for precisely defined, highly visible and sufficiently bright light marks which form a defined reference angle, for example, in a leveled Cartesian coordinate system of a multiaxis construction laser.
Beam splitters are optical components whose optically reflecting surfaces are formed at least partially planar and, therefore, discretely deflect a focused light beam or discretely divide parallel light beams.
In contrast, cylindrical lenses are optical components the optical refraction surfaces of which are formed at least partially as a cylindrical jacket and, therefore, continuously deflect a focused light beam within a plane or continuously expand a light beam. Because of the cylindrical shape, the intensity for transmitted, parallel-polarized light near the edge and, therefore, of the deflected line beam decreases steeply as the expansion angle increases. A deflecting angle of 90° cannot be achieved in practice. In addition, diffraction effects prevent a sharply defined limitation of the deflection angle.
According to U.S. Pat. No. 5,363,469, a prismatic lens has a cylindrical central area and two concave lateral areas which limit the expansion angle in a defined manner by total internal reflection of edge portions of the light beam without splitting the light beam into discrete partial beams.
According to U.S. Pat. No. 543,730, an optical beam splitter for a light beam that is parallel along a beam axis has a plane-parallel transparent central area and a plurality of reflecting reflector surfaces that are inclined by 45° to the beam axis so that spot beams can be generated perpendicular to one another.
Further, according to U.S. Pat. No. 6,005,719, the parallel light beam in a multiaxis construction laser is discretely deflected with beam splitter gratings within two planes perpendicular to one another so that two rows of discretely divided spot beams are formed. It is also disclosed that the use of a cylindrical lens for continuous expansion of a focused light beam within a plane is disadvantageous.
Further, according to U.S. Pat. No. 5,838,431, the parallel light beam in a rotating construction laser is continuously expanded within a plane as a linear beam with a greater brightness along the axis by a prismatic combination lens with a plane-parallel transparent area and a cylindrical segment-shaped area smoothly adjoining the latter. A discrete splitting of the light beam into spot beams that are deflected in a predetermined manner is not possible.
It is an object of the invention to provide an optical beam splitter for generating a plurality of discrete spot beams with a defined reference angle and a linear beam which is continuously expanded in a plane.